18F fluoroethylations: different strategies for the rapid translation of 11C-methylated radiotracers

IntroductionThe translation of 11C-labeled compounds into their respective 18F-labeled derivatives is an important tool in the rapid development of positron emission tomography (PET) tracers. Thus, our aim was the development of a general method for the preparation of 18F-fluoroethylated compounds that (a) is applicable to a variety of precursors, (b) can be performed in a fully automated commercially available synthesizer and (c) enables this rapid translation of 11C-methylated tracers into their 18F-fluoroethylated analogs sharing the same precursor molecules.MethodsTen methods for the preparation and purification of different 18F-fluoroethylating agents were compared. Subsequently, five 18F-labeled PET tracers were synthesized under fully automated conditions.ResultsRadiochemical yields ranged from 34.4% to 60.8%, and time consumption ranged from 20 to 55 min for all methods. Use of 1-bromo-2-[18F]fluoroethane and distillation evinced as the method of choice.ConclusionsWe were able to develop a general method for the preparation of a variety of 18F-fluoroethylated molecules. The provided tool is solely based on commercially available resources and has the potential to simplify and accelerate innovative PET tracer development in the future.